This invention relates to a wicket dam lifting assembly and in particular, the invention relates to a removable hydraulic lifting module for a wicket dam which is removably mounted as a unit from the wet cylinder chamber in the sill.
This invention relates to a wicket dam assembly, and, in particular, to an apparatus for aligning the lifting cylinder and the wicket.
This invention relates to a wicket dam assembly, and, in particular to a prop for supporting the wicket having a weak link for facilitating a controlled failure under excessive loads.
Wicket dams are employed to establish and maintain the height of navigable waterways. Such dams operate by moving wickets or gates to an elevated position, the upper end of which establishes the minimum height of the waterway. Vessels are moved around the dam by means of a system of locks. When the water level is high as in times of Spring runoff and heavy rain, the level of the waterway is sometimes raised to the level of the upper edge of the wicket. Under such circumstances, the wicket gate is retracted and traffic bypasses the locks.
A gate is a hinged structure which is pivoted between retracted and elevated positions at the upper end of the dam spillway or sill. In its retracted position, the wicket lies generally horizontally along the river bottom or sill. In its elevated position, the wicket is disposed near the vertical at an angle of about 65.degree. to 70.degree..
A lifting mechanism in the form of a hydraulic lifting cylinder engages a bearing on the back side of the gate to lift it into position. Known lifting mechanisms for relatively small wicket dams employ a hydraulic cylinder which is pivotable about an axis parallel to the spillway and the pivot axis of the gate. The method for raising such a wicket uses a lifting cylinder oriented at an angle so that the bearing or lifting point is always in line with the piston rod once the wicket is set in its raised position. However, in large constructions, such known arrangements do not provide sufficient maneuverability for the hydraulic lift cylinder. Thus, the size of the wicket which can be lifted is limited. In addition, the known design has a problem, such that, if the wicket should for some reason lower prematurely, the piston rod would not be in alignment and the wicket could not be easily raised. Under such circumstances, an auxiliary lifting means, such as a lifting barge upstream of the dam, is required to reposition the wicket.
It is inevitable that repair and maintenance of the lifting cylinder is required on a periodic basis. Thus, if repairs cannot be effected quickly at the site, removal of the equipment is necessary. In known arrangements, the cylinder must be partially or fully disassembled if it is to be removed from the site. Such disassembly often requires opening of hydraulic lines in the wet cylinder chamber below the dam sill which is difficult. The known arrangements are therefore difficult to maintain and repair. Further, because the environment presents a danger to repair crews working on the sill, it is desirable to remove the equipment for repair or maintenance at a site remote from the dam. Presently, there is no means available to quickly remove and replace the hydraulic lifting system from the sill.
The lifting cylinder is in a harsh environment subject to damage from falling debris and silt carried by the waterway. Accordingly, protection for the lifting cylinder mechanism is desirable.
Wickets are held aloft by a device known as a prop. The prop is typically hinged to the back side of the wicket and the prop rotates about an axis parallel to the gate axis. The free end of the prop rides along a track guide known as a hurter on the sill floor. When the gate is lifted from the retracted, horizontal position, the prop slides along the hurter until it engages a check point or bearing against which it rests. The wicket may be lowered by lifting it to raise the wicket further and thereby release the prop in a known manner.
The prop structure is susceptible to damage when overloaded. If a large vessel, such as a loose barge, moves against the wicket, the prop will break away. Under such circumstances, damage to the wicket and the prop can be considerable. Realizing that the prop may be overloaded, it is desirable to provide a weak point in the prop which will fail in a controlled manner and which is more easily repaired.